Hypercholesterolemia is one of main causes of coronary heart disease(CHD). Clinical trials demonstrated that lowering serum cholesterol levels would reduce incidence of new cardiovascular events and mortality by primary or secondary preventions. The objective of this retrospective study was to compare efficacy and side effects of lovartatin and simvastatin in treatement of hypercholesterolemia. In Boramae Hospital, patients were included when they have taken lovastatin 20 mg or simvastatin 10 mg for 52 weeks with laboratory monitoring for cholesterol at baseline, 3, 6 and 12 month period. As results, total 128 outpatients were included with their total cholesterol level <240 mg/dl and triglyceride level <400 mg/dl at baseline. Total cholesterol and LDL cholesterol of lovastatin group (n=60) and simvastatin group (n=68) were significantly reduced from baseline (p=0.001). Lovastatin maximally reduced total cholesterol by $23.9\%,;triglyceride;by;12.3\%$, LDL cholesterol by $36.1;\%$ and increased HDL cholerterol by $7.8\%$ and simvastatin reduced by $24.1\%,;20.5\%,;34.3\%;respectively$ and HDL increased by $11.2\%$. There were no significant differences between lovastatin and simvastatin in mean percent change of lipid levels at 12, 24 and 52 weeks from baseline. Cumulative percentage of patients reaching the target LDL cholesterol concentration by 24 weeks was $61.7\%$ in lovastatin and $64.7\%$ in simvastatin. Average time to reach the target LDL goal was 100.1 days in lovastatin and 99.8 days in simvastatin. Both lovastatin and simvastatin also significantly reduced total cholesterol and LDL cholesterol in all subgroups (diabetes mellitus, hypertension, and coronary heart disease). In this study, treatment efficacy in patients with coronary heart disease was lower than other patients. Considering clinical importance of secondary prevention, more intensive treatment is necessary to decrease LDL cholesterol level of 100 mg/dl or lower in patients with coronary heart disease or other clinical atherosclerotic disease. There were no serious side effects during the study period. Digestive side effects were most frequently reported (lovastatin $8.3\%;vs;simvastatin;8.8\%$). In conclusion, both lovastatin and simvastatin were similar in lipid lowering effects and there was no difference in incidence of side effects.